The present invention relates generally to inflatable cushions used in vehicle occupant restraint systems. More particularly, this invention relates to a cushion constructed from two opposed fabric panels of different sizes, each of which is in the shape of the same polygon. The panels are joined along their respective perimeter portions by folding the perimeter portions of the larger panel to create lapped panel portions that are secured to the perimeter portions of the smaller panel, preferably by chemical securing means. In a preferred embodiment, certain perimeter portions of the larger polygon panel are removed to produce a smooth lapped area comprising a single layer of overlapped or underlapped fabric without multiple folded layers formed by excess fabric.
An inflatable restraint cushion, or air bag, plays an important role in protecting the occupants of a vehicle from injury due to collision against the car body. Typically, the air bag is disposed within a supporting structure such as a dash panel, steering wheel, door panel, or other fixed portion of a car body in opposed or adjacent relationship to a seat in the vehicle. When inflated rapidly by the pressure of a reaction gas released from an inflator during a collision, the air bag serves as a protective barrier between the vehicle occupant and the steering wheel or other portion of the vehicle against which the occupant might otherwise be thrown.
Air bags have been used in the past to protect both the vehicle operator and vehicle passengers. Systems for the protection of the vehicle operator are typically mounted in the steering column of the vehicle and utilize cushion constructions that deploy directly towards the driver. These xe2x80x9cdriver-sidexe2x80x9d air bags can be of a relatively simple configuration in that they function over a relatively small, well-defined area between the driver and the steering column.
As used herein, it is intended that the following terms be defined as indicated: A xe2x80x9cpolygonxe2x80x9d is a plane geometric figure having n sides and n vertices. An equiangular polygon is one in which all the angles comprising the vertices are equal. An equilateral polygon is one in which all sides are of equal length. A regular polygon is one that is both equiangular and equilateral. A convex polygon is one in which no side, if extended, will enter the polygon. Unless otherwise specified, the term xe2x80x9cpolygonxe2x80x9d shall refer to a convex equiangular polygon. The term xe2x80x9cfabricxe2x80x9d shall be used in a broad sense to describe any woven or non-woven fabric, as well as any film, polymer, combinations or composites thereof, or other material from which the individual panels comprising an air bag may be constructed. Additionally, reference to the use of adhesives shall refer to the use of chemical, thermal, or other bonding or fusing methods.
Typically, air bags designed for the protection of vehicle drivers are circular or substantially circular in shape when viewed from the front or the back. Such circular air bags are constructed by superimposing, aligning, and seaming or joining of two similarly-dimensioned circular panels along their respective coincident perimeter edges, thereby forming an equatorial seam, after such circular panels have been separately cut from a blank of suitable air bag fabric. A problem with conventional circular air bags is that, upon inflation and impact, these equatorial seams are exposed to substantial tensile stresses that can cause failure of the seam. This invention addresses the problem of the possible failure of a conventional equatorial seam subjected to such tensile stresses.
To better understand this invention, it is necessary to define the terms used herein to describe the various aspects of its construction. In accordance with the teachings of this invention, two fabric panels of different size are cut from a fabric blank and attached to each other around their respective perimeters. For purposes of discussion herein, the panel area nearest the edge or perimeter of each panel shall be termed the perimeter border area of the panel.
The term xe2x80x9cfoldxe2x80x9d is intended to mean a bending over, with or without the formation of a crease. If at least a portion of the perimeter border area of the larger panel is folded over the corresponding perimeter border area of the smaller panel, thereby enclosing and concealing the cut edge of the smaller panel, it is said that an overlap is formed. If at least a portion of the perimeter border area of the larger panel is folded under the corresponding perimeter border area of the smaller panel, thereby leaving the edge of the smaller panel exposed, it is said that an underlap is formed. The term xe2x80x9clappedxe2x80x9d is intended to mean either overlapped or underlapped. The term xe2x80x9clapped panel portionxe2x80x9d or xe2x80x9clapped panel areaxe2x80x9d or xe2x80x9clapped areaxe2x80x9d is intended to mean the perimeter border area of the smaller panel that is lapped by the larger panel. The secured area is the area of the lapped panel portion, preferably substantially all of the lapped panel portion, over which the perimeter border area of the larger and smaller panels have been joined or attached by adhesive means.
The term xe2x80x9cfold widthxe2x80x9d is intended to have its common meaning as applied to the flap or folded portion of the larger panel, and may be more technically defined as the radial distance, prior to folding, between the perimeter of a given side of the n-sided polygon comprising the larger panel and the corresponding fold axis on that same side. Fold width should be distinguished from xe2x80x9cfold length,xe2x80x9d which would be measured parallel to the edge of the polygon (and would generally be equal to the length of the side n of the n-sided polygon). The term xe2x80x9cconcentricxe2x80x9d or xe2x80x9csuperimposedxe2x80x9d refers to the arrangement of the panels, such that the geometric centers of the two panels are aligned and coincident, and the corresponding n sides of the two polygons comprising the panels are parallel.
The air bag of the present invention may be produced by superimposing two polygon-shaped panels of differing size, folding at least portions of the perimeter border area of the larger panel over or under corresponding perimeter border areas of the smaller panel to create lapped panel portions, and securing together the lapped panel portions, preferably by adhesive means. It should be noted that the lapped area may comprise substantially the entire width of the folded panel portion, or merely some part thereof, as will be described herein.
Attachment of the perimeter portions of the panels using suitable adhesive means as are known by those skilled in the art eliminates the need for sewing the air bag as part of the assembly procedure. Sewing without substantial seam lapping typically produces a narrow seam, with discrete points of attachment, over which the substantial stresses of inflation and impact are manifested as tensile forces. Adhesive seaming with substantial seam lapping of the kind described herein produces a relatively wide seam area with a relatively continuous area of attachment, over which the substantial stresses of inflation and impact are manifested as shear forces. In so doing, a common tendency of adhesive seaming to fail when subjected to peeling forces may be avoided, and a fully functional and reliable seam may be constructed with little chance of rupture or leakage.
In addition, while conventional circular air bags are functionally effective, the circular shape of the front and back fabric sections from which the air bags are constructed does not lend itself to the efficient utilization of fabric during the manufacturing process. Specifically, the arrangement of these circular pieces on a given blank of air bag fabric does not result in efficient fabric utilization or yield. It has been found that fabric utilization can be significantly improved by substituting polygon shapes, and particularly equiangular polygons having at least five sides, for the circular-shaped panels of the prior art. The polygon shapes can be placed in either adjoining or close proximity to one another on the fabric blank from which they are cut to provide common (coincident) or nearly common (closely adjacent) sides or cut edges, thus minimizing fabric waste and cost and providing a useful advancement over the present art. Because the face and rear portions of the air bag of the present invention are constructed from polygon-shaped panels of different size, separate blanks (or separate areas of the same blank) for each panel size may be used so that all panels of a given size can be most economically arranged on a given area in accordance with the teachings herein.
The advantages, therefore, of the present invention include increased seam strength and reliability due to the chemical seaming of the lapped panel portions, and better fabric utilization due to the alignment of polygon shapes on a fabric blank. Accordingly, this invention is believed to represent a useful advancement over the present art.
In view of the foregoing, it is an object of this invention to provide a simple inflatable cushion restraint or air bag that is fabricated without sewing and that may be used in a system for restraining a vehicle occupant in the event of a collision, as well as a related process for manufacturing such an air bag.
It is another object of this invention to provide a vehicle occupant restraint cushion or air bag that can be formed by lapping and securing the perimeter portions of two polygonal fabric panels of different size in a way that distributes the stresses of inflation and impact within an area larger than that associated with a conventional sewn equatorial seam.
In accordance with one aspect of the present invention, the cushion or air bag of the instant invention comprises a first polygon-shaped fabric panel, a somewhat differently sized second fabric panel (larger or smaller) that has the same polygon shape and that is superimposed onto said first panel in concentric relation such that the respective outside edges of the two panels are parallel, and gas inlet and outlet means for introducing and expelling an inflating medium within the cavity formed by the first and second fabric panels. In a preferred embodiment, first and second fabric panels are each comprised of a panel of fabric in the shape of the same n-sided equiangular polygon, having a perimeter comprised of a sequence of linear segments separated by vertices or corner portions disposed therebetween, where n is at least five, i.e., both of the panels are configured in the shape of the same equiangular pentagon, hexagon, heptagon, octagon, or the like. The two panels are of different size, so that, when superimposed to form a flat, layered structure with coincident centers, the perimeter border arear of the larger panel extends laterally beyond the perimeter border area of the smaller panel. The seam area is constructed by folding, along each of the n sides, the perimeter border area of the larger panel over or under the corresponding perimeter border area of the smaller panel. The resulting lapped area is then adhesively joined by chemical, thermal, or other means. It is contemplated that additional layers of fabric or other materials may be interposed or placed alongside one or both of the layers, either fully or partially, as the design specifications may dictate. Upon appropriate inflation, the resulting flat cavity forms a restraint cushion or air bag that, when incorporated into an appropriate air bag system, is suitable for protecting the occupants of a vehicle involved in a collision.
In accordance with another aspect of the present invention, a method for forming the inflatable cushion of the present invention is provided. Where two separate panels are used, the method comprises the steps of: (a) cutting a first fabric panel in a chosen n-sided polygon shape; (b) cutting a second fabric panel in the same chosen n-sided polygon shape, but of a size that is somewhat larger or smaller than the first fabric panel; (c) superimposing the first and second panels in concentric relationship, thereby forming a two-layered structure in which portions of the perimeter border areas of the larger panel laterally extend beyond the perimeter border areas of the smaller panel; (d) folding, along each of the n sides, at least a portion of the extended perimeter border areas of the larger panel over or under the corresponding perimeter border areas of the smaller panel, thereby forming a lapped panel portion; and (e) adhesively joining together the two overlapping or underlapping layers comprising the lapped panel portion along each of the n sides of the polygon.
Since the panels are of different size, radial cuts may be made along the edge of the larger panel to accommodate the folding of the lapped panel portions of the larger panel. In a preferred embodiment, a small triangular-shaped section of fabric may be removed from corner locations along the perimeter of the larger panel to avoid the folding or bunching of excess fabric. Both the cutting and joining operations may be achieved by manual or automated methods known by those skilled in the art. As is conventionally done, suitable holes may be cut in the rear panel to form gas inlet means, gas outlet means, or for other purposes; and various other structural devices or reinforcements may be incorporated into the design of the air bag.